I have some yeast cultures frozen in my parents' chest freezer. I haven't pulled one to see if it is viable but I assume as long as they never thawed they should be fine. I'll have to pull a sample next time I visit and see how it works out.

I have some yeast cultures frozen in my parents' chest freezer. I haven't pulled one to see if it is viable but I assume as long as they never thawed they should be fine. I'll have to pull a sample next time I visit and see how it works out.

I'm willing to bet that they are still alive.

__________________Slots Down BreweryStick with the plan....not the sparge.

Just a small update. I just got done freezing my yeast for the year and decided to do a little qualitative testing while I was at it. I used three different strenght glycerine solutions this time. 35% 50% and 60%. My plan is to see if different levels of glycerine affect the lag time when making the first step of starter from frozen yeast. If more glycerine = shorter lag time then I will assume that more glycerine = more viable yeast surviving the freeze. If I observe no appreciable difference, then I will stay with my current assumption that the yeast are just sluggish after freezing and need more time to regain activity. If Brewitt does some viability assays for us and contributes that information, then we should have a pretty good idea of what to expect from freezing yeast at home.

__________________Slots Down BreweryStick with the plan....not the sparge.

Got my pressure cooker this week with some glycerine.
Just finished testing it by canning 7 qts of water and pressure cooking it (I will now have sterile water on hand for a while). I also did a 50:50 glycerine/water in 2x 4oz jars (only filled halfway, so yeast can occupy the other half). Next weekend I will be bottling and I plan on freezing washed yeast.

If Brewitt does some viability assays for us and contributes that information, then we should have a pretty good idea of what to expect from freezing yeast at home.

Sorry for the delay in doing some experimentation on this. Work has been quite busy and I have had no time for side projects. I will prep a starter this week and set up some frozen preparations at a few glycerin concentrations from 15 to 60% and at -30C and -80C. It will probably be a couple weeks before I know anything about viability since it requires cell counts and colony counts.

That would be great!
I had good results with 30% glycerin solution, and I think that success with smaller concentration will depend on how well is glycerin mixed with slurry.. but experiment will give more relevant informations about that.